However, my general guidance is usually to work backward.

As a start work backward from the NOI and determine a cap rate. 

I really like your idea of working backward.  

Work backwards and see what is left over.

Answer those two questions and work backwards from there :) Best of luck to you! 

Along with constant moving.. many of these tenants at least in that market will simply move annually they know the landlords will bend over backwards for a 100% voucher so they just pack up the few things they have an move to a freshly renovated house and leave their old house behind..

They may not make much progress, and they may even go backwards.

We could work backwards from the condo's upper tier pricing (that you would likely get into contract at) and backwards calculate how much income you're going to need to qualify given the probability of how the rest of your rental income and liabilities will be caluclated.We do these calculations (plan A, B, C, etc) on a daily basis.

Pencil this in backwards and see where you are in relation to your lon-term goals.....this could be salvaged with patience and smarts.

Buying a property at 7-8% interest today, then having to refi again in 12-18 months at a cost of $3,000-5,000 when rates are back down in perhaps the 5% range is likely taking a step backwards financially.